Traveling wave strip line antenna



Jan. 31, 1967l J. G. HOFFMAN 3,302,207

TRAVELING WAVE STRIP LINE ANTENNA Filed Feb. 28, 1964 F/G./ F1613 JOHN G. HOFFMAN l2 Fl G 2 I4 INVENTOR BYQMQMQ ATTORNEY United States Patent O 3,302,207 TRAVELING WAVE STRIP LINE ANTENNA John G. Hoffman, Riverside, Calif., assigner to the United States of America as represented by the Secretary of the Navy Filed Feb. 28, 1964, Ser. No. 348,919 4 Claims. (Cl. 343-731) The invention herein described may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

The present invention relates to antennas and more particularly to an improved flush-mounted high-frequency antenna for -use with high velocity aircraft and the like.

With the advent of high velocity aircraft the need for ush-mounted antennas became imperative. The present antenna functions to fulfill that need; it is light Weight and very thin in thickness as compared to conventional waveguide antennas, and can be used where standard waveguide slot arrays would be impractical due to their size and weight.

The present invention is a flush-mounted antenna having a long axial slot and means to control the look angle of the antenna. A zig-zag -center conductor is located in close proximity to the slot for exciting the slot and crosses the axial centerline of the slot at right angles to provide maximum etliciency of excitation.

The antenna of the present invention is quite different from the dual dipole type antenna disclosed in U.S. Patent No. 2,990,547, which .has a zig-zag conductive element mounted flush within an elongated slot and backed by a reilective cavity, wherein the zig-zag element forms a main part of the antenna radiating structure. Whereas in the present invention, which is not a dipole antenna, the zigzag center conductor is entirely behind the radiating structure and is used for exciting the radiating slot, and is not a portion of the radiating structure.

It is an object of the invention to provide a novel traveling wave strip line antenna.

Another object of the invention is to provide a compact light-weight flush-mounted antenna.

A further object of the invention is to provide a leaky wave strip line antenna in which the antenna look angle can be controlled.

Other objects and many of the attendant advantages of this invention will become readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 is a top view of an embodiment of the invention showing an elongated antenna slot of varying slot Width.

FIG. 2 is a cross sectional view along line 2-2 of FIG. 1.

FIG. 3 is a bottom view of the antenna of FIG. 1 showing the zig-zag -center conductor.

A traveling wave antenna is characterized by a traveling wave mode that propagates along a guiding structure with an attenuation coefficient that varies along the direction of propagation along the guiding wave structure. The leakage or loss of energy is in the form of radiation. This radiation is at a maximum angle of 6, which is given approximately by the formula:

wavelength in free space Cosme effective wavelength of the guiding structure ICC strip line arrangement. However, as shown in the drawings, this invention provides excitation of a traveling wave slot 10 by running a zig-Zag center conductor 12 behind and along the length of the slot such that the center conductor is perpendicular to the axial center line of slot 10 at each cross over point. As a result, the guiding structure is a slow wave structure. By controlling the number and spacing `of the zig-zags of conductor 12, the antenna look angle and maximum direction of radiation can be controlled. Conductor 12 in the present antenna, therefore, is -used to both excite slot 10 and to correct for the phase velocity along the antenna to obtain the desired look angle.

As shown in FIG. 2, slot 10 is formed in a suitable conductive surface 11, which can `be a separate metallic sheet or the outer skin of an aircraft or .missile if desired, and the Zig-Zag center conductor 12 is located in close proximity to, but separated by a dielectric layer 14, from the slot. Dielectric 14 may be any suitable insulating material or an air gap, to suit the desired needs. The exposed side of conductor 12 may also be covered with a protective dielectric layer if desired.

The attenuation coefcient along the rguiding structure 11 is varied by Varying the Width of slot 10, since variation .in slot Width is necessary in order to obtain the desired antenna distribution or ybest beamwidth tosidelobe ratio.

The present antenna is compact and light weight and especially lends itself readily to production techniques by photoetching process. The present antenna also provides a leaky wave antenna in strip line wherein the antenna look angle can be controlled which is usually not the case in a traveling wave antenna.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specically described.

What is claimed is:

1. A traveling-wave stripline antenna comprising:

(a) a substantially at guiding wave structure for flush mounting thereof,

(b) at least one radiation slot in said guiding structure,

(c) a Zig-zag center conductor mounted directly behind said slot for exciting the slot,

(d) the number and spacing of the zig-Zags of said center conductor controlling the antenna look angle and direction of radiation.

2. A traveling-wave strip-line antenna comprising:

(a) a substantially fiat guiding wave structure for flush mounting thereof,

(b) a traveling-wave axial slot,

(c) a zig-zag center conductor mounted directly behind said slot for exciting the slot,

(d) said center conductor being insulated from said flat wave guiding structure by .a thin dielectric layer,

(e) the number and spacing of the zig-zags of said center conductor controlling the antenna look angle and direction of radiation.

3. A traveling-wave strip-line antenna comprising:

(a) a substantially at guiding wave structure for flush mounting thereof,

(b) at least one radiation slot in said guiding structure,

(c) a Zig-zag center conductor mounted directly behind said slot for exciting the slot,

(d) said zigzag center conduct-or crossing perpendicular to the `axial centerline of said slot a plurality of times,

(e) the number land spacing -of the zi-g-zags of said center conductor controlling the antenna look angle and direction of radiation.

S3 4 4. A travelingawave strip-line antenna comprising: distribution and back to zero width along the length (a) a substantially flat guiding Wave structure for ush thereof.

mounting thereof, (b) a traveling-wave axial Slot, d 1 b h d References Cited by the Examiner (c) a zig-Zag center conductor mounte direct y e in 5 said slot for exciting the slot, UNITED STATES PATENTS (d) said center conductor being insulated from said at 2,654,842 10/ 1953 Engelmann 343-770 wave `guiding structure by a thin dielectric layer, 2,816,285 12/ 1957 Topol 343-770 (e) the number and spacing Vof the Zig-zags of said 2,990,547 6/ 1961 McDougal 343--767 center conductor controlling the vantenna look angle 10 and direction of radiation, ELI LIEBERMAN, Primary Examiner.

(f) the attenuation coeicient along said antenna being varied by varying the Width of said radiating slot CHESTER L' JUSTUSExammer' from zero to a maximum Width for desired antenna R, E. BERGER, Assistant Examiner, 

1. A TRAVELING-WAVE STRIP-LINE ANTENNA COMPRISING: (A) A SUBSTANTIALLY FLAT GUIDING WAVE STRUCTURE FOR FLUSH MOUNTING THEREOF, (B) AT LEAST ONE RADIATION SLOT IN SAID GUIDING STRUCTURE, (C) A ZIG-ZAG CENTER CONDUCTOR MOUNTED DIRECTLY BEHIND SAID SLOT FOR EXCITING THE SLOT, (D) THE NUMBER AND SPACING OF THE ZIG-ZAG''S OF SAID CENTER CONDUCTOR CONTROLLING THE ANTENNA LOOK ANGLE AND DIRECTION OF RADIATION. 